The invention relates to an engine lubricating system and more particularly to an improved system for lubricating an engine to insure against the draining of lubricant into the engine when the engine is not running and also to insure equal distribution of the lubricant.
A lubricating system has been proposed which has particular utility in conjunction with two cycle internal combustion engines wherein an engine driven pump pumps a fixed amount of lubricant during each cycle of its operation. The amount of lubricant actually supplied to the engine is controlled by a delivery valve that is solenoid operated and moveable between a delivery position wherein lubricant is delivered directly from the pump to the engine and a non-delivery position wherein the lubricant is pumped back to the system somewhere upstream of the inlet of the pump. The amount of lubricant supplied is adjusted by varying the duty cycle of the solenoid operated delivery valve. A system of this general type is disclosed in the co-pending application entitled "Lubricating Oil Supplying System For Two Cycle Engine", Ser. No. 862,984, filed Apr. 7, 1992 in the name of Yoshinobu Yashiro, which application is assigned to the Assignee hereof. The disclosure of that application is incorporated herein by reference.
Although this type of lubricating system is extremely effective in providing good lubrication control and, accordingly, minimizing the amount of emissions of smoke and other harmful constituents in the exhaust gases, there is some risk that when the engine is shut down, lubricant may flow to the engine past the delivery valve. This possibility exist because of the fact that lubricant normally flows from the lubricant tank to the pump by gravity and hence the tank is positioned at a higher level than the pump. Also, the provision of the return line to the supply valve gives rise to another flow path through which lubricant may leak back to the engine. If this leakage occurs, then the engine will emit smoke on initial starting and its exhaust gases will contain a high percentage of hydrocarbons.
It is, therefore, a principal object to this invention to provide an improved lubricating system of this type wherein leakage of lubricant to the engine when the engine is not running is avoided.
It is a further object to this invention to provide an improved lubricating system for an internal combustion engine of the type employing a delivery valve and in which the flow of lubricant past the delivery valve to the engine when the engine is not running is precluded.
In conjunction with lubricating system of this type, frequently the lubricant is delivered to the engine at more than one location. When this is done, frequently it is the practice to employ plural delivery valves, each controlling the amount of lubricant delivered to the respective lubrication point. When this is done, however, it is desirable to minimize the number of return conduits. However, if the return conduits are merged together, then the return from one delivery valve may upset or adversely affect the operation of the other delivery valve.
It is, therefore, a still further object to this invention to provide an improved lubricating system of the type employing plural delivery valves and wherein the flow restriction in the return lines for all delivery valves is substantially the same.